JPH0339106B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for surface treatment of polymer webs. More particularly, it relates to an improved vacuum glow discharge process. BACKGROUND ART Conventionally, surface treatments such as corona discharge treatment, ultraviolet irradiation treatment, vacuum glow discharge treatment, and wireless polar discharge treatment have been performed on plastic films, metal plates, and the like in order to improve their surface characteristics. Among these surface treatment methods, vacuum glow discharge treatment is disclosed, for example, in Japanese Patent Publication No. 35-7578,
As seen in Publication No. 10336, etc., it has been widely used to improve the adhesive strength, hydrophilicity, dyeability, etc. of polymer surfaces. However, when attempting to obtain the desired surface properties by surface treatment using these methods, the polymer is directly exposed to the activated plasma atmosphere, and the web transport, which is further exposed to the activated plasma and heated up, is required. A phenomenon was observed in which the temperature of the web to be processed increased unnecessarily due to contact with the processing roll. As described in JP-A No. 53-129262, for example, in the field of photographic materials, coloring of the processed material is strictly limited, and in order to obtain the desired adhesion, the coloring of the processed material is strictly limited. It is particularly necessary to control the temperature within a certain desired range. Additionally, if the polymer temperature rises unnecessarily, non-crystalline polymers such as polystyrene will undergo significant thermal shrinkage, impairing the flatness of the web, making it unsuitable for practical use. It becomes possible. In addition, even in the case of biaxially stretched crystalline polyester such as polyethylene terephthalate, if the temperature is increased unnecessarily, partial thermal relaxation and thermal denaturation will occur, resulting in loss of flatness of the processed web and low molecular weight (monomer, oligomer, etc.)
is precipitated on the web surface and the transparency is impaired, so it cannot be put to practical use. Furthermore, if the temperature of the web to be processed rises unnecessarily, the following disadvantages may occur. In general, polymers that are not thermosetting resins, such as polystyrene and polyethylene terephthalate, have a lower modulus of elasticity due to their viscoelastic properties as the temperature rises, making them susceptible to loose deformation due to external forces. In other words, if the material to be processed is wound up at an unnecessarily high temperature, wrinkles are likely to occur, although the degree varies depending on the tension at the time of winding, or there may be differences in the thickness of the original sheet. The thicker portions are transferred, resulting in various surface failures. Furthermore, the mobility and activity of active radicals generated when the polymer processing object is exposed to an active plasma atmosphere increases due to unnecessary temperature rise, resulting in recrystallization. There is also a concern that the desired surface properties imparted to the material may be impaired by exposure to the plasma atmosphere. As is clear from the above description, in vacuum glow discharge treatment, if the temperature of the object to be treated rises above the desired temperature, or if it is wound up and stored at a high temperature for a long period of time, various problems such as those mentioned above will occur. It turns out. An object of the present invention is to provide a surface treatment method that can prevent the various surface failures described above without impairing adhesion. As a result of intensive research, the present inventors have discovered that both adhesiveness and flatness are not impaired by heating up the polymer web by subjecting it to vacuum glow discharge treatment or by bringing the polymer web into contact with several cooling rolls. Ta. At this time, the most important thing is how to set the temperature of the polymer web cooled by the cooling roll. In other words, the initial temperature of the polymer after glow discharge treatment is
If T ₀ [℃] is the temperature of the polymer web immediately after being cooled by the nth cooling roll, T _o [℃] is the temperature of the polymer web immediately after being cooled by the nth cooling roll.
To satisfy T _o ≧T _o-1 −40 (n is a positive integer),
In other words, the polymer web cooled by the cooling rolls must be cooled sequentially so that the temperature difference is 40° C. or less. However, if the polymer web has a glass transition temperature T _g or lower, it may be rapidly cooled to room temperature all at once. When the polymer web has a glass transition temperature T _g or higher, if it is cooled with a temperature difference of 40°C or more,
Differences in thermal dimensional changes within the plane of the polymer become noticeable, causing plane failures such as single-sided and flat-sided failures. In addition, rapid thermal contraction on the cooling roll causes scratches, which is undesirable. Next, the content of the present invention will be explained in more detail with reference to the drawings. In FIG. 1, 1a and 1b are discharge rod-shaped electrodes provided at regular intervals, 2 is a high voltage current 3 is a polymer web feeding part, 4 is a polymer web winding part, 5 is a polymer web,
6, 7, 8, 9, 10, 11 are guide rolls, 1
2 is a vacuum chamber, 13 is an insulating plate for holding an electrode, 14 is a ground, 15 is an exhaust port, 16 is a vacuum pump, and 17 is a leak valve for adjusting the degree of vacuum in the vacuum chamber 12 by introducing outside air. 18 is a preheating drive roll, and 19 is a cooling roll. The polymer web 5 fed out from the delivery section 3 while being preheated by the preheat drive roll 18 is first subjected to discharge treatment on one side by the discharge electrode 1a, then reversed by the guide rolls 6 and 7, and then the other side is The surface is subjected to discharge treatment by the discharge electrode 16. Thereafter, the polymer web 5 is subjected to a cooling treatment according to the present invention by cooling rolls 19a, 19b, and 19c, and then wound up in a winding section 4. As the cooling rolls 19a, 19b, 19c,
The cooling rolls 19a, 19a, 19a, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 19b, 22b, 23b, 23c, 23d,34,34 for4 32, 40, 30, 40, 40, 19b,
The temperature of 19c can be set separately. Assuming that the temperature conditions of the cooling rolls 19a, 19b, and 19c are T ₁ [°C], T ₂ [°C], and T ₃ [°C], respectively, and the initial temperature of the polymer web after discharge treatment is T ₀ [°C], the glass The gist of the present invention is to satisfy T ₁ ≧T ₀ -40; T ₂ ≧T ₁ -40; _{T 3} ≧T ₂ -40 in the temperature range above the transition temperature. As long as it is below the transition temperature, T ₃ can be set without being limited to the above formula. When the above conditional expression is not satisfied, as described above, plane failures such as one-sided cracks and corners, and scratches occur. If the above conditional expressions are satisfied, these failures can be prevented, but if the temperature difference is extremely reduced, the number of cooling rolls will increase, resulting in an increase in equipment investment and an expansion in the scale of the equipment, which is not preferable. There is no problem if the circumferential speed of the cooling rolls 19a, 19b, and 19c is normally set to the conveyance speed of the polymer web, but when cooling a polymer web that has a large thermal contraction, it is necessary to cool the polymer web gradually, taking into account the thermal contraction of the polymer web. It is preferable to reduce the roll diameter to prevent scratches that occur during conveyance. If the diameter of the cooling roll is designed so that the contact time with the polymer web is 1.5 seconds or more, the temperature of the polymer web can be brought to approximately the set temperature of the cooling roll. In order to further clarify the effects of the present invention, examples will be introduced below. Example 1 In the device shown in Figure 1, the cross section has a diameter of 3 cm.
Four 40cm cylindrical bar electrodes were fixed at 10cm intervals in a vacuum chamber, and a biaxially stretched polyester film 100μ thick and 30cm wide was placed on the surface for 2 seconds at a distance of 15cm from the electrode surface and directly facing the electrode surface. I ran it so that it could be processed. Power was applied to the above electrode so that the polyester film received an energy of 200 Watt·min/m ² . The pressure inside the tank at this time is
The discharge frequency was 0.3 Torr and 10 Kdl. When the polyester film after passing through the discharge treatment zone was measured with an infrared thermometer installed in the tank, it showed a temperature of 145°C. The glass transition temperature of the polyester film used is 80°C. Therefore, according to the present invention, above the glass transition temperature, the polyester film
3 were set at 110°C, 75°C, and 20°C, respectively, so that they would not be cooled due to a temperature difference of 40°C or more, and if they were below the glass transition temperature, they would be cooled all at once to room temperature.
When the polyester web was brought into contact with a book cooling roll for 2 seconds each, the temperatures of the polyester web at each time point were 112°C, 80°C, and 28°C, respectively. In this way, a polyester web sample was prepared which was wound with a tension of 2 kg. On the other hand, a sample that was subjected to the same discharge treatment and showed a temperature of 145°C was wound up without any cooling. Furthermore, the temperature setting of the three cooling rolls was changed to 95.
℃, 50℃, and 20℃, and rolled samples were prepared under the same operation. , , for each sample, one edge, small bevel, scratch, and adhesion (dry and wet processing)
The evaluation was carried out by the following method. B. As shown in Figure 2, place a 20cm long sample parallel to the left edge of the 30cm wide sample at a position 15mm from the left edge of the sample.
Make one notch and place it on a horizontal surface. Second
In the figure, if the left side of the cut line is L and the right side is R, then in a sample where a single cut line has occurred, R and L will no longer match by making the cut. The distance between R and L was measured, and the one-sided gap was evaluated based on its size. (b) Small surface: A grade is given to a surface with no visible minute irregularities when visually inspected under the reflected light of a fluorescent lamp.
Those that occur almost on the entire surface are classified as C class, and those in between these are classified as B class. Scratches When visually inspected under reflected light from tungsten light, those with no scratches were classified as A grade, those with scratches occurring almost on the entire surface were graded as C grade, and those in between these were graded as B grade. D. Adhesion test during drying Each of the samples mentioned above was coated with a conventional gelatin-silver halide photographic emulsion for squirrel-sensitive materials, and the level of adhesion was tested. To determine the level of adhesion, use a razor to make 6 square cuts in the vertical and horizontal directions on the emulsion side of the prepared silver halide photographic film, and then apply adhesive tape (Nitto Polyester Tape) on top of this. The adhesive tape was peeled off by hand in a direction of 180°, and the adhesive strength was ranked A, B, or C based on how the emulsion film peeled off. A means that it will not peel off at all, B means that it will peel off partially, and C means that it will peel off completely. E. Adhesion test during wet processing For each of the samples mentioned above, two scratches were made with a metal pencil on the emulsion surface of the film in the processing solution at each stage of development, fixing, and washing. If the emulsion layer did not peel off more than the scratches, it was graded A. If the maximum peeling was within 5 mm, it was graded B. If it was larger than this, it was graded C. . The evaluation results are shown in Table 1.

[Table] As is clear from the above results, it can be seen that the desired flatness and adhesiveness can be obtained by the present invention. The present invention is not limited to the embodiments, and the present invention is not limited to the embodiments. The idea of the present invention can be applied to a wide range of applications.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an apparatus for carrying out the vacuum glow discharge surface treatment method of the present invention, and FIG. 2 is an explanatory diagram of an example evaluation method of the present invention. DESCRIPTION OF SYMBOLS 1, 1a, 1b... Electrode for discharge, 5... Polymer web, 12... Vacuum chamber, 16... Vacuum pump, 19
a, 19b, 19c... cooling roll.

Claims (1)

[Claims] 1. After vacuum glow discharge treatment of the polymer web, T _o ≧T _o-1 in a temperature range equal to or higher than the glass transition temperature.
-40 (n is a positive integer). However, T ₀ is the initial temperature [° C.] of the polymer web after the discharge treatment, and T _o is the temperature [° C.] of the polymer web after passing through the n-th cooling roll.